Data transmission method and device, network equipment, and terminal equipment

Abstract

An embodiment of the present application provides a data transmission method and apparatus, a network device, and a terminal device. The method includes: after the target base station receives a switching confirmation message sent by the terminal device, the target base station sends data of a first service to the terminal device, and the switching confirmation message is used to indicate that the terminal device confirms switching from a source base station to the target base station; wherein the data of the first service is sent on the source base station side via multicast, and the data of the first service is sent on the target base station side via multicast or unicast.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of mobile communication technology, and specifically to a data transmission method and apparatus, network equipment, and terminal equipment. Background Art

[0002] In order to improve the efficiency of air interface data transmission, the network can decide whether to use unicast or multicast to send service data to the terminal device. During the movement of the terminal device, the terminal device may switch from a base station that supports multicast to another base station that does not support multicast. In this case, how to ensure the continuity of service data needs to be solved. Summary of the invention

[0003] The embodiments of the present application provide a data transmission method and apparatus, a network device, and a terminal device.

[0004] The data transmission method provided in the embodiment of the present application includes:

[0005] After the target base station receives the switching confirmation message sent by the terminal device, it sends the data of the first service to the terminal device, and the switching confirmation message is used to indicate that the terminal device confirms the switching from the source base station to the target base station; wherein the data of the first service is sent on the source base station side via multicast, and the data of the first service is sent on the target base station side via multicast or unicast.

[0006] The data transmission method provided in the embodiment of the present application includes:

[0007] The terminal device receives data of the first service sent by the source base station in a multicast manner;

[0008] After the terminal device switches from the source base station to the target base station, it sends a switching confirmation message to the target base station and receives data of the first service sent by the target base station in a multicast or unicast manner.

[0009] The data transmission device provided in the embodiment of the present application is applied to a target base station, and the device includes:

[0010] A receiving unit, configured to receive a handover confirmation message sent by a terminal device; the handover confirmation message is used to indicate that the terminal device confirms handover from a source base station to a target base station;

[0011] A sending unit is used to send data of the first service to the terminal device; wherein the data of the first service is sent by multicast at the source base station side, and the data of the first service is sent by multicast or unicast at the target base station side.

[0012] The data transmission device provided in the embodiment of the present application is applied to a terminal device, and the device includes:

[0013] A receiving unit, configured to receive data of a first service sent by a source base station in a multicast manner;

[0014] a sending unit, configured to send a handover confirmation message to the target base station after handover from the source base station to the target base station;

[0015] The receiving unit is further configured to receive data of the first service sent by the target base station in a multicast manner or a unicast manner.

[0016] The network device provided in the embodiment of the present application includes a processor and a memory. The memory is used to store a computer program, and the processor is used to call and run the computer program stored in the memory to execute the above-mentioned data transmission method.

[0017] The terminal device provided in the embodiment of the present application includes a processor and a memory. The memory is used to store a computer program, and the processor is used to call and run the computer program stored in the memory to execute the above-mentioned data transmission method.

[0018] The chip provided in the embodiment of the present application is used to implement the above-mentioned data transmission method.

[0019] Specifically, the chip includes: a processor, which is used to call and run a computer program from a memory, so that a device equipped with the chip executes the above-mentioned data transmission method.

[0020] The computer-readable storage medium provided in the embodiment of the present application is used to store a computer program, which enables a computer to execute the above-mentioned data transmission method.

[0021] The computer program product provided in the embodiment of the present application includes computer program instructions, which enable a computer to execute the above-mentioned data transmission method.

[0022] The computer program provided in the embodiment of the present application, when executed on a computer, enables the computer to execute the above-mentioned data transmission method.

[0023] Through the above technical solution, before switching, the terminal device receives the data of the first service sent by the source base station via multicast; after switching, the terminal device receives the data of the first service sent by the target base station via multicast or unicast, thereby realizing the continuity of the service data during multicast transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0025] Figure 1 is a schematic diagram of a communication system architecture provided by an embodiment of the present application;

[0026] Figure 2 is a network architecture diagram of a point-to-multipoint transmission mechanism provided in an embodiment of the present application;

[0027] Figure 3 A flowchart of a data transmission method provided in an embodiment of the present application;

[0028] Figure 4 A handover preparation flow chart provided in an embodiment of the present application;

[0029] Figure 5 A switching execution flow chart provided in an embodiment of the present application;

[0030] Figure 6 The structure of the data transmission device according to the embodiment of the present application is shown in FIG. Figure 1 ;

[0031] Figure 7 The structure of the data transmission device according to the embodiment of the present application is shown in FIG. Figure 2 ;

[0032] Figure 8 is a schematic structural diagram of a communication device provided in an embodiment of the present application;

[0033] Fig. 9 is a schematic structural diagram of a chip according to an embodiment of the present application;

[0034] Fig.10 It is a schematic block diagram of a communication system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] The following will describe the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0036] The technical solutions of the embodiments of the present application can be applied to various communication systems, such as: Long Term Evolution (LTE) system, LTE Frequency Division Duplex (FDD) system, LTE Time Division Duplex (TDD) system, 5G communication system or future communication system, etc.

[0037] For example, the communication system 100 used in the embodiment of the present application is as follows: Figure 1 As shown. The communication system 100 may include a network device 110, which may be a device that communicates with a terminal 120 (or referred to as a communication terminal, terminal). The network device 110 may provide communication coverage for a specific geographical area, and may communicate with terminals located within the coverage area. Optionally, the network device 110 may be an evolved base station (eNB or eNodeB) in an LTE system, or a wireless controller in a cloud radio access network (CRAN), or the network device may be a mobile switching center, a relay station, an access point, a vehicle-mounted device, a wearable device, a hub, a switch, a bridge, a router, a network side device in a 5G network, or a network device in a future communication system, etc.

[0038] The communication system 100 also includes at least one terminal 120 located within the coverage of the network device 110. As used herein, "terminal" includes but is not limited to connecting via a wired line, such as via a Public Switched Telephone Networks (PSTN), a Digital Subscriber Line (DSL), a digital cable, a direct cable connection; and / or another data connection / network; and / or via a wireless interface, such as, for a cellular network, a Wireless Local Area Network (WLAN), a digital television network such as a DVB-H network, a satellite network, an AM-FM broadcast transmitter; and / or another terminal configured to receive / send communication signals; and / or an Internet of Things (IoT) device. A terminal configured to communicate via a wireless interface may be referred to as a "wireless communication terminal", "wireless terminal" or "mobile terminal". Examples of mobile terminals include, but are not limited to, satellite or cellular telephones; Personal Communications System (PCS) terminals that may combine cellular radiotelephones with data processing, fax, and data communications capabilities; PDAs that may include radiotelephones, pagers, Internet / Intranet access, Web browsers, notepads, calendars, and / or Global Positioning System (GPS) receivers; and conventional laptop and / or palmtop receivers or other electronic devices that include radiotelephone transceivers. A terminal may refer to an access terminal, User Equipment (UE), a subscriber unit, a subscriber station, a mobile station, a mobile station, a remote station, a remote terminal, a mobile device, a user terminal, a terminal, a wireless communication device, a user agent, or a user device. The access terminal can be a cellular phone, a cordless phone, a Session Initiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, a Personal Digital Assistant (PDA), a handheld device with wireless communication capabilities, a computing device or other processing device connected to a wireless modem, a vehicle-mounted device, a wearable device, a terminal in a 5G network, or a terminal in a future evolved PLMN, etc.

[0039] Optionally, the terminals 120 may perform device-to-device (D2D) communication.

[0040] Optionally, the 5G communication system or 5G network may also be referred to as a New Radio (NR) system or NR network.

[0041] Figure 1 One network device and two terminals are shown exemplarily. Optionally, the communication system 100 may include multiple network devices and each network device may include another number of terminals within its coverage area, which is not limited in the embodiments of the present application.

[0042] Optionally, the communication system 100 may also include other network entities such as a network controller and a mobility management entity, which is not limited in the embodiments of the present application.

[0043] It should be understood that the device with communication function in the network / system in the embodiment of the present application can be referred to as a communication device. Figure 1 Taking the communication system 100 shown as an example, the communication equipment may include a network device 110 and a terminal 120 with communication functions. The network device 110 and the terminal 120 may be the specific devices described above and will not be repeated here. The communication equipment may also include other devices in the communication system 100, such as a network controller, a mobile management entity and other network entities, which is not limited in the embodiments of the present application.

[0044] It should be understood that the terms "system" and "network" are often used interchangeably in this article. The term "and / or" in this article is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0045] To facilitate understanding of the technical solutions of the embodiments of the present application, the technical solutions related to the embodiments of the present application are described below.

[0046] In the 5G system, a point-to-multipoint transmission mechanism will be introduced. The network architecture of this transmission mechanism is as follows: Figure 2As shown in the figure, the network architecture includes the following network elements: Radio Access Network (RAN) nodes, Access and Mobility Management Function (AMF), Session Management Function (SMF), User Plane Function (UPF), Network Exposure Function (NEF), Policy Control Function (PCF), Application Function (AF). It should be noted that Figure 2 The network architecture shown is only exemplary, and the network architecture may also include more or fewer other network elements. The network side uses a point-to-multipoint transmission method to send service data in the service area (Service Area) of the multicast service. Terminal devices in this service area can use a multicast tunnel to receive service data.

[0047] The 5G core network (5GC) supports the Protocol Data Unit (PDU) connection service, which refers to the service of exchanging PDU data packets between terminal devices and data networks (DN). The PDU connection service is implemented by the establishment of a PDU session initiated by the terminal device. After a PDU session is established, a data transmission channel is established between the terminal device and the DN.

[0048] The subscription information of each single-network slice selection assistance information (S-NSSAI) may include a default data network name (Data Network Name, DNN) and multiple DNNs. When the terminal device initiates a PDU session establishment request and does not provide the DNN of the S-NSSAI, the AMF will select the default DNN for its S-NSSAI (provided that the subscription information of the S-NSSAI has a default DNN); if there is no default DNN, the AMF will select the locally configured DNN for the S-NSSAI. If the DNN carried by the terminal device in the PDU session establishment request message is not supported by the network, and the AMF fails to select a suitable SMF by querying the NF Repository Function (NRF), the AMF will reject the PDU session establishment request and carry the reason value in the rejection message: DNN is not supported.

[0049] Each PDU session supports a PDU session type, and the PDU session type can be one of the following: IPv4 type, IPv6 type, IPv4v6 type, Ethernet type, and unstructured type.

[0050] The PDU session is established, modified, and released between the terminal device and the SMF through the Non Access Layer (NAS) Session Management (SM) signaling.

[0051] On the other hand, the network can also trigger the establishment of a PDU session. Specifically: 1) When the application server wants to establish a PDU session connection, it will send a trigger message to 5GC; 2) When 5GC receives the PDU session establishment request from the application server, it will send a message to the terminal device to trigger the establishment of the PDU session; 3) After receiving the message, the terminal device will send it to the corresponding application on the terminal device; 4) The application on the terminal device decides when to initiate the specified PDU session connection based on the content of the trigger message.

[0052] When the terminal device sends a PDU session establishment request message to the network, it provides a PDU session identifier. Here, the PDU session identifier is assigned by the terminal device and is unique within the terminal device. In order to support switching between 3GPP and non3GPP access in different networks, the PDU session identifier will be stored in the Unified Data Management (UDM). Whether it is 3GPP access or non-3GPP access, the terminal device establishes multiple PDU session connections connected to the same DN, or multiple PDU session connections connected to different DNs. The terminal device can establish multiple PDU session connections connected to the same DN, and connect to the DN through different UPFs. Optionally, when the terminal device establishes multiple PDU session connections, the SMF corresponding to each PDU session connection may be different. The service SMF information of each PDU session connection will be registered in the UDM.

[0053] When a terminal device establishes a PDU session, a PDU session is established for the same service. This PDU session can support both unicast transmission of service data and multicast transmission of service data.

[0054] In the data interface (i.e., N3 interface) between the core network and the RAN, a terminal device-specific N3 channel can be used, and both unicast data and multicast data for this terminal device are transmitted in this specific channel. A shared transmission channel can also be used, and this transmission channel is shared by multiple terminals for data transmission, and these multiple terminals can belong to the same group. In order to improve the efficiency of air interface data transmission, the network can decide whether to use unicast or multicast to send service data to the terminal device. During the movement of the terminal device, the terminal device may switch from a base station that supports multicast to another base station that does not support multicast. In this case, how to ensure the continuity of service data needs to be solved. To this end, the following technical solution of the embodiment of the present application is proposed to achieve continuity of support for multicast services.

[0055] It should be noted that, in the technical solution of the embodiment of the present application, the description of "multicast" can also be replaced by "groupcast" or "broadcast".

[0056] It should be noted that, in the technical solution of the embodiments of the present application, the description of "base station" can also be replaced by "cell" or "RAN node".

[0057] It should be noted that in the technical solution of the embodiment of the present application, the description of "tunnel" can also be replaced by "channel" or "connection".

[0058] Figure 3A flow chart of a data transmission method provided in an embodiment of the present application is shown in FIG. Figure 3 As shown, the data transmission method includes the following steps:

[0059] Step 301: The terminal device receives data of the first service sent by the source base station via multicast.

[0060] In the embodiment of the present application, the source base station refers to the base station that serves the terminal device before the handover. The target base station refers to the base station that serves the terminal device after the handover. Furthermore, the types of the source base station and the target base station can be the same or different. For example, both the source base station and the target base station are gNBs. For example, the source base station is an eNB and the target base station is a gNB.

[0061] Here, the data of the first service is sent in a multicast manner at the source base station side, that is, the source base station supports multicast data sending (or supports sending the data of the first service in a multicast manner).

[0062] Step 302: After the terminal device switches from the source base station to the target base station, it sends a switching confirmation message to the target base station and receives data of the first service sent by the target base station via multicast or unicast.

[0063] Here, after the target base station receives the switching confirmation message sent by the terminal device, it sends the data of the first service to the terminal device, wherein the switching confirmation message is used to indicate that the terminal device confirms the switching from the source base station to the target base station; the data of the first service is sent on the target base station side via multicast or unicast.

[0064] In the embodiment of the present application, the data of the first service is sent on the source base station side through a multicast manner, which is equivalent to: the data of the first service is sent on the source base station side through a multicast session.

[0065] In the embodiment of the present application, the data of the first service is sent on the target base station side through a multicast mode or a unicast mode, which is equivalent to: the data of the first service is sent on the target base station side through a multicast session or a unicast session.

[0066] It should be noted that a "multicast session" refers to a PDU session used to transmit multicast service data (i.e., a PDU session that transmits service data in a multicast manner). A "unicast session" refers to a PDU session used to transmit unicast service data (i.e., a PDU session that transmits service data in a unicast manner).

[0067] In the embodiment of the present application, before sending data of the first service, the target base station needs to establish a PDU session of the first service, and the PDU session can be a multicast session or a unicast session. The following describes the context of the target base station obtaining the PDU session in different situations.

[0068] Case 1: The target base station receives a first message sent by a core network element, where the first message includes the context of the multicast session.

[0069] In an optional manner, the core network element is SMF.

[0070] In an optional manner, the first message is an N2 SM message. Further, optionally, the first message carries an indication information, and the indication information is used to indicate that the N2 SM message is for multicast transmission.

[0071] After the target base station obtains the context of the multicast session, if the target base station supports sending the data of the first service in a multicast manner, the data of the first service is sent in a multicast manner on the target base station side.

[0072] For a case where the data of the first service is sent by multicast at the source base station side, and the data of the first service is sent by multicast at the target base station side:

[0073] 1) If the multicast session already exists on the target base station side, the context of the multicast session includes at least one of the following: an identifier of the terminal device, a group identifier of the multicast group to which the terminal device belongs, an identifier of the multicast session, and multicast quality of service (QoS) flow information; or,

[0074] 2) If the multicast session does not exist on the target base station side, the context of the multicast session includes at least one of the following: the identifier of the terminal device, the group identifier of the multicast group to which the terminal device belongs, the identifier of the multicast session, multicast QoS flow information, N3UP address, and the tunnel identifier associated with the multicast session.

[0075] Here, the tunnel identifier associated with the multicast session refers to the core network tunnel ID (CN Tunnel ID) of the UPF associated with the multicast session.

[0076] Here, the multicast QoS flow information refers to QoS parameters related to the multicast QoS flow.

[0077] Case 2: The target base station receives a second message sent by a core network element, where the second message includes the context of the unicast session.

[0078] In an optional manner, the core network element is SMF.

[0079] In an optional manner, the second message is an N2 SM message. Further, optionally, the second message carries an indication information, and the indication information is used to indicate that the N2 SM message is for unicast transmission.

[0080] After the target base station obtains the context of the unicast session, the data of the first service is sent by the target base station in a unicast manner (the target base station supports the unicast manner by default).

[0081] In the case where the data of the first service is sent by multicast at the source base station side, and the data of the first service is sent by unicast at the target base station side:

[0082] The context of the unicast session includes at least one of the following: an N3UP address, a tunnel identifier associated with the unicast session, and unicast QoS flow information.

[0083] Here, the tunnel identifier associated with the unicast session refers to the core network tunnel ID (CN Tunnel ID) of the UPF associated with the unicast session.

[0084] Here, the unicast QoS flow information refers to QoS parameters related to the unicast QoS flow.

[0085] Case three: the target base station receives a third message sent by a core network element, where the third message includes a context of a multicast session and a context of a unicast session.

[0086] In an optional manner, the core network element is SMF.

[0087] In an optional manner, the third message is an N2 SM message.

[0088] After the target base station obtains the context of the unicast session and the multicast session, the data of the first service can be sent in a unicast manner or in a multicast manner on the target base station side. Specifically,

[0089] 1) If the target base station supports the multicast session and accepts the multicast session, the target base station sends first indication information to the core network element, where the first indication information is used to instruct the target base station to accept the multicast session and reject the unicast session. Accordingly, the target base station sends data of the first service in a multicast manner.

[0090] 2) If the target base station does not support the multicast session or does not accept the multicast session, the target base station sends second indication information to the core network element, where the second indication information is used to indicate that the target base station does not support the multicast session or does not accept the multicast session. Correspondingly, the target base station sends data of the first service in a unicast manner.

[0091] Further, optionally, the target base station may store the context of the multicast session; or, the target base station may also delete the context of the multicast session.

[0092] 3) The target base station stores the context of the multicast session and the context of the unicast session; if the target base station uses the context of the multicast session, the target base station sends a third indication message to the core network network element, and the third indication message is used to instruct the target base station to use the context of the multicast session (correspondingly, the target base station sends the data of the first service via multicast); or, if the target base station uses the context of the unicast session, the target base station sends a fourth indication message to the core network network element, and the fourth indication message is used to instruct the target base station to use the context of the unicast session (correspondingly, the target base station sends the data of the first service via unicast).

[0093] In the embodiment of the present application, before the target base station receives the handover confirmation message sent by the terminal device, the service server sends the data of the first service to the source base station, and the source base station can choose to forward the data of the first service to the target base station by multicast or by unicast. The following describes how the data of the first service is forwarded between the source base station and the target base station.

[0094] I) Method 1

[0095] The target base station receives a multicast QoS flow from a service server forwarded by the source base station, and the multicast QoS flow contains data of the first service; if the target base station does not support the multicast QoS flow, the target base station discards or rejects the multicast QoS flow, or the target base station converts the multicast QoS flow into a unicast QoS flow and sends it to the terminal device.

[0096] II) Method 2

[0097] The target base station receives a unicast QoS flow sent by the source base station, where the unicast QoS flow includes data of the first service; wherein the unicast QoS flow is obtained by converting a multicast QoS flow from a service server by a core network element.

[0098] III) The target base station receives a unicast QoS flow sent by the source base station, where the unicast QoS flow contains data of the first service; wherein the unicast QoS flow is obtained by the source base station converting a multicast QoS flow from a service server.

[0099] In an embodiment of the present application, the target base station and the source base station may be asynchronous in sending data streams. In order to ensure that the terminal device can compensate for this asynchrony, the PSA UPF can insert a sequence number (Series Number, SN) into the data packets sent to the source base station and the target base station. Specifically, the target base station receives a first data stream forwarded by the source base station from a service server, and receives a second data stream sent by the service server through a multicast tunnel; the data packets in the first data stream carry a first SN, and the data packets in the second data stream carry a second SN; wherein the first data stream and the second data stream belong to the data stream of the first service.

[0100] Here, if the first SN is equal to the second SN, it means that the first data stream and the second data stream are synchronized. If the first SN is not equal to the second SN, it means that the first data stream and the second data stream are different. The following describes how to schedule data streams to compensate for the asynchrony in the case of asynchrony.

[0101] A) If the first SN is smaller than the second SN, the target base station schedules a third data stream for the terminal device through a unicast tunnel, and the third data stream carries a third SN; the rate of the third data stream is greater than the rate of the first data stream; when the third SN is equal to the second SN, the target base station schedules the second data stream for the terminal device through a multicast tunnel.

[0102] B) If the first SN is smaller than the second SN, the target base station schedules a third data stream for the terminal device through a multicast tunnel, and the third data stream carries a third SN; the rate of the third data stream is greater than the rate of the first data stream; when the third SN is equal to the second SN, the target base station schedules the second data stream for the terminal device through a multicast tunnel.

[0103] C) If the first SN is greater than the second SN, the target base station performs repeated detection on the first data stream and the second data stream through a Packet Data Convergence Protocol (PDCP) entity to generate a third data stream; the target base station schedules the third data stream for the terminal device through a multicast tunnel.

[0104] The technical solution of the embodiment of the present application is described below in conjunction with a specific switching interaction process.

[0105] Figure 4 A schematic diagram of a handover preparation process provided in an embodiment of the present application is shown in FIG. Figure 4 As shown, the process includes the following steps:

[0106] Step 400: The source base station decides to trigger redirection via the N2 interface.

[0107] Step 401: The source base station sends a handover request message to the source AMF.

[0108] Here, the handover request message carries at least one of the following information: an identifier of a target base station (Target ID), a transparent container from a source base station to a target base station (Source to Target transparent container), an N2 SM message list (N2SM info list), and a PDU session identifier.

[0109] Here, the PDU session identifier refers to the identifier of the PDU session to be switched to the target base station, that is, the identifier of the multicast session.

[0110] In this embodiment, the source base station forwards the QoS flow (QoS Flows) to the target base station, which can be implemented in the following ways:

[0111] 1) The source base station ignores the capabilities of the target base station and directly transfers the multicast QoS flow to the target base station. If the target base station does not support the multicast QoS flow, the target base station may discard or reject the multicast QoS flow, or treat the multicast QoS flow as a unicast QoS flow (provided that the unicast QoS flow meets the QoS requirements).

[0112] 2) When the source base station knows the capabilities of the target base station, if it is determined that the target base station does not support multicast QoS flows, the multicast QoS flows will not be forwarded to the target base station. During path switching, the SMF converts the multicast QoS flows into unicast QoS flows and sends them to the target base station.

[0113] 3) When the source base station learns the capabilities of the target base station, if it determines that the target base station does not support multicast QoS flows, it does not forward the multicast QoS flows to the target base station. During path switching, the source base station converts the multicast QoS flows into unicast QoS flows and sends them to the target base station.

[0114] 4) The source base station only forwards the unicast QoS flow to the target base station.

[0115] Step 402: The source AMF selects a target AMF.

[0116] Here, when the source AMF cannot serve the UE, the source AMF selects the target AMF.

[0117] Step 403: The source AMF sends a UE context establishment request message (i.e., Namf_Communication_CreateUEContext Request) to the target AMF.

[0118] Step 404: The target AMF sends an SM context update request message (ie, Nsmf_PDUSession_UpdateSMContext Request) to the SMF.

[0119] Here, the SM context update request message carries at least one of the following information: the identifier of the target base station, the PDU session identifier, the target AMF identifier, and the N2 SM message (N2 SM Information).

[0120] Here, optionally, the SM context update request message further carries indication information, where the indication information is used to indicate the PDU session of the multicast session and / or related information of the multicast session (such as the group address, the group ID).

[0121] Step 405: SMF selects UPF (PSA).

[0122] Here, when the target base station does not support multicast mode, the SMF generates an N2 SM message, and the N2 SM message includes at least one of the following information: N3UP address, UPF tunnel identifier, and QoS parameters. Further, optionally, the N2 SM message also carries an indication information, and the indication information is used to indicate that the N2 SM message is for the target base station and / or the N2 SM message is for unicast transmission.

[0123] Here, the SMF confirms whether the N2 switch (for the indicated PDU session) is received based on the target base station's identification and / or the requested multicast session information. If the UPF changes, the SMF selects the UPF (PSA) that supports the multicast session.

[0124] Step 406a: SMF sends a session modification request message (ie, N4 Session ModificationRequest) to UPF (PSA).

[0125] Step 406b: UPF (PSA) sends a session modification response message (ie, N4 Session ModificationResponse) to SMF.

[0126] Step 406c: The SMF sends a session establishment request message (ie, N4 Session EstablishmentRequest) to the target UPF.

[0127] Step 406d: The target UPF sends a session establishment response message (ie, N4 Session EstablishmentResponse) to the SMF.

[0128] It should be noted that, for the case of multicast switching to multicast (i.e., the source base station adopts the multicast mode and the target base station adopts the multicast mode): if the multicast session (or the uplink text of the multicast session) already exists on the target base station side, the above steps 405 to 406d can be omitted. If the multicast session (or the uplink text of the multicast session) does not exist on the target base station side, the multicast session is established through the above steps 405 to 406d.

[0129] Step 407: SMF sends an SM context update response message (ie, Nsmf_PDUSession_UpdateSMContext Response) to the target AMF.

[0130] Step 408: PDU Handover Response supervision is performed between the target AMF and the target UPF.

[0131] Step 409: The target AMF sends a handover request message to the target base station.

[0132] Here, the messages exchanged between the above steps 407 to 409 may carry at least one of the following information: N2 SM message, PDU session identifier.

[0133] Step 410: The target base station sends a handover request confirmation message to the target AMF.

[0134] Step 411a: The target AMF sends an SM context update request message (ie, Nsmf_PDUSession_UpdateSMContext Request) to the SMF.

[0135] Step 411b: SMF sends a session modification request message (ie, N4 Session ModificationRequest) to the target UPF.

[0136] Step 411c: The target UPF sends a session modification response message (ie, N4 Session ModificationResponse) to the SMF.

[0137] Step 411d: SMF sends a session modification request message (ie, N4 Session ModificationRequest) to the source UPF.

[0138] Step 411e: The source UPF sends a session modification response message (ie, N4 Session ModificationResponse) to the SMF.

[0139] Step 411f: SMF sends an update SM context response message (i.e., Nsmf_PDUSession_UpdateSMContext Response) to the target AMF.

[0140] Step 412: The target AMF sends a UE context establishment response message (i.e., Namf_Communication_CreateUEContext Response) to the source AMF.

[0141] In an optional manner, the SMF may choose to establish a multicast session context or a unicast session context for the target base station.

[0142] 1) For the case of multicast switching to multicast (i.e., the source base station adopts the multicast mode and the target base station adopts the multicast mode): If the multicast session (or the uplink text of the multicast session) already exists on the target base station side, the SMF carries at least one of the following information to the target base station in the N2 SM message: UE ID, the group identifier of the multicast group to which the UE belongs, the identifier of the multicast session, and the multicast QoS flow information. If the multicast session (or the uplink text of the multicast session) does not exist on the target base station side, the SMF carries at least one of the following information to the target base station in the N2 SM message: UE ID, the group identifier of the multicast group to which the UE belongs, the identifier of the multicast session, the multicast QoS flow information, the N3UP address, and the tunnel identifier of the UPF associated with the multicast session.

[0143] 2) For the case of switching from multicast to unicast (i.e., the source base station adopts multicast and the target base station adopts unicast): SMF carries at least one of the following information to the target base station in the N2 SM message: N3UP address, tunnel identifier of UPF associated with the unicast session, and unicast QoS flow information.

[0144] In another optional manner, the SMF provides the target base station with the context of the multicast session and the unicast session (for example, the context is sent to the target base station via an N2 SM message). If the target base station can support and accept multicast sessions, the target base station instructs the SMF to accept the multicast session and reject the unicast session. Alternatively, the target base station stores the context of the two sessions and indicates to the SMF whether the session it uses is a multicast session or a unicast session. Further, if the target base station does not support or does not accept multicast sessions, the SMF is instructed that it does not support or accept multicast sessions, and the target base station can store or delete the context of the multicast session.

[0145] Figure 5 A schematic diagram of the handover execution process provided in the embodiment of the present application, such as Figure 5 As shown, the process includes the following steps:

[0146] Step 501: The source AMF sends a handover command to the source base station.

[0147] Here, the switching command carries at least one of the following information: a transparent container from the target base station to the source base station (Target to Source transparent container), an identifier of a PDU session to be switched, and an identifier of a PDU session that failed to be established.

[0148] Here, the PDU session identifier to be switched can be Figure 4 The PDU session identifier in the N2 SM information from the target base station in the handover preparation process shown.

[0149] Step 502: The source base station sends a handover command to the UE.

[0150] Here, the handover command carries a UE container, which is a container belonging to the UE part in the transparent container from the target base station to the source base station. The UE container is transparently transmitted from the target base station to the source base station via the AMF, and is sent by the source base station to the UE.

[0151] Step 502a: The source base station performs uplink RAN ​​status transfer (Uplink RAN ​​Status Transfer) to the source AMF.

[0152] Step 502b: N1N2 message transmission (ie, Namf_Communication_N1N2Message Transfer) is performed between the source AMF and the target AMF.

[0153] Step 502c: The target AMF performs downlink RAN ​​status transfer (Downlink RAN ​​Status Transfer) to the target base station.

[0154] Step 503a: The source base station performs direct data forwarding to the target base station.

[0155] Step 503b: The source base station performs indirect data forwarding to the target base station via the source UPF.

[0156] Here, uplink packets are sent from the target base station to the target UPF and UPF (PSA). Downlink packets are sent from UPF (PSA) to the source base station via the source UPF, and the source base station starts forwarding downlink packets to the target base station, which can be done by direct forwarding (such as step 3a) or indirect forwarding (such as step 3b).

[0157] Step 504: The UE sends a handover confirmation message (Handover Confirm) to the target base station.

[0158] Here, after the UE is successfully synchronized to the target base station, the UE sends a handover confirmation message to the target base station, and the message indicates that the UE confirms that the handover is successful.

[0159] For asynchronous data transmission between the source base station and the target base station, the UPF (PSA) may insert the SN into the data packets transmitted to the source base station and the target base station.

[0160] 1) During the handover, the source base station forwards the data packet carrying the SN to the target base station.

[0161] 2) After the switch, if the SN of the data packet forwarded by the target base station from the source base station is smaller than the SN of the data packet in the multicast tunnel, the target base station and / or UPF (PSA) first schedules data to the UE through the unicast tunnel. When the SN of the data packet in the unicast tunnel is equal to the SN of the data packet in the multicast tunnel, it switches to the multicast tunnel to schedule data to the UE.

[0162] 3) After the handover, if the SN of the data packet forwarded by the target base station from the source base station is greater than the SN of the data packet in the multicast tunnel, the target base station and / or UPF (PSA) schedules data to the UE through the multicast tunnel and performs duplicate detection at the PDPC layer.

[0163] It should be noted that it can be assumed here that the SN range (ie, the difference between the SN of the data packet forwarded by the source base station and the SN of the data packet in the multicast tunnel) can cover the buffer size of the UPF (PSA).

[0164] It should be noted that, considering the storage cost of UPF (PSA) and the satisfaction of multicast QoS requirements, there is no significant difference in the SN range (ie, the difference between the SN of the data packet forwarded by the source base station and the SN of the data packet in the multicast tunnel).

[0165] Step 505: The target base station sends a switching notification message to the target AMF.

[0166] The handover notification message indicates that the target base station confirms that the handover is successful.

[0167] Step 506a: The target AMF sends an N2 information notification (ie, Namf_Communication_N2InfoNotify) to the source AMF.

[0168] Step 506b: The source AMF sends an N2 information notification confirmation (i.e., Namf_Communication_N2InfoNotify Ack) to the target AMF.

[0169] Step 506c: The source AMF sends a SM context release request message (ie, Nsmf_PDUSession_ReleaseSMContext Request) to the SMF.

[0170] Step 507: The target AMF sends an SM context update request message (ie, Nsmf_PDUSession_UpdateSMContext Request) to the SMF.

[0171] Step 508a: The SMF sends a session modification request message (ie, N4 Session ModificationRequest) to the target UPF.

[0172] Step 508b: The target UPF sends a session modification response message (ie, N4 Session ModificationResponse) to the SMF.

[0173] Step 509a: The SMF sends a session modification request message (ie, N4 Session ModificationRequest) to the source UPF.

[0174] Step 509b: The source UPF sends a session modification response message (ie, N4 Session ModificationResponse) to the SMF.

[0175] Step 510a: SMF sends a session modification request message (ie, N4 Session ModificationRequest) to UPF (PSA).

[0176] Step 510b: UPF (PSA) sends a session modification response message (ie, N4 Session ModificationResponse) to SMF.

[0177] Step 511: SMF sends an update SM context response message (ie, Nsmf_PDUSession_UpdateSMContext Response) to the target AMF.

[0178] Step 512: The UE performs a registration process with the network.

[0179] Step 513a: SMF sends a session release request message (ie, N4 Session ReleaseRequest) to the source UPF.

[0180] Step 513b: The source UPF sends a session release response message (ie, N4 Session ReleaseResponse) to the SMF.

[0181] Step 514a: The source AMF sends a UE context release command (ie, UE Context Release Command) to the source base station.

[0182] Step 514b: The source base station sends a UE context release command completion message (ie, UE Context Release Command Complete) to the source AMF.

[0183] Step 515a: The SMF sends a session modification request message (ie, N4 Session ModificationRequest) to the target UPF.

[0184] Step 515b: The target UPF sends a session modification response message (ie, N4 Session ModificationResponse) to the SMF.

[0185] It should be noted that the above application Figure 4 and Figure 5 In the process shown, the data (or data packet) refers to the data (or data packet) of the first service, wherein the first service may be any service, such as a video service.

[0186] Figure 6 The structure of the data transmission device according to the embodiment of the present application is shown in FIG. Figure 1 , applied to the target base station, such as Figure 6 As shown, the data transmission device includes:

[0187] The receiving unit 601 is used to receive a handover confirmation message sent by a terminal device; the handover confirmation message is used to indicate that the terminal device confirms handover from the source base station to the target base station;

[0188] The sending unit 602 is used to send data of the first service to the terminal device; wherein the data of the first service is sent by multicast at the source base station side, and the data of the first service is sent by multicast or unicast at the target base station side.

[0189] In an optional manner, the data of the first service is sent on the source base station side through a multicast session, and the data of the first service is sent on the target base station side through a multicast session or a unicast session.

[0190] In an optional manner, the receiving unit 601 is further configured to receive a first message sent by a core network element, where the first message includes the context of the multicast session.

[0191] In an optional manner, the data of the first service is sent by multicast at the source base station side, and the data of the first service is sent by multicast at the target base station side:

[0192] If the multicast session already exists on the target base station side, the context of the multicast session includes at least one of the following: an identifier of the terminal device, a group identifier of the multicast group to which the terminal device belongs, an identifier of the multicast session, and multicast QoS flow information; or,

[0193] If the multicast session does not exist on the target base station side, the context of the multicast session includes at least one of the following: the identifier of the terminal device, the group identifier of the multicast group to which the terminal device belongs, the identifier of the multicast session, multicast QoS flow information, N3UP address, and the tunnel identifier associated with the multicast session.

[0194] In an optional manner, the receiving unit 601 is further configured to receive a second message sent by a core network element, where the second message includes the context of the unicast session.

[0195] In an optional manner, the data of the first service is sent on the source base station side in a multicast manner, and the data of the first service is sent on the target base station side in a unicast manner:

[0196] The context of the unicast session includes at least one of the following: an N3UP address, a tunnel identifier associated with the unicast session, and unicast QoS flow information.

[0197] In an optional manner, the receiving unit 601 is further configured to receive a third message sent by a core network element, where the third message includes a context of a multicast session and a context of a unicast session.

[0198] In an optional manner, the sending unit 602 is also used to send a first indication message to the core network element if the target base station supports the multicast session and accepts the multicast session, and the first indication message is used to instruct the target base station to accept the multicast session and reject the unicast session.

[0199] In an optional manner, the sending unit 602 is also used to send second indication information to the core network element if the target base station does not support the multicast session or does not accept the multicast session, and the second indication information is used to indicate that the target base station does not support the multicast session or does not accept the multicast session.

[0200] In an optional manner, the device further includes:

[0201] A processing unit (not shown in the figure) is used to store the context of the multicast session; or to delete the context of the multicast session.

[0202] In an optional manner, the device further includes:

[0203] a processing unit (not shown in the figure), configured to store the context of the multicast session and the context of the unicast session;

[0204] The sending unit 602 is also used to send third indication information to the core network network element if the target base station uses the context of the multicast session; the third indication information is used to instruct the target base station to use the context of the multicast session; or, if the target base station uses the context of the unicast session, send fourth indication information to the core network network element, the fourth indication information is used to instruct the target base station to use the context of the unicast session.

[0205] In an optional manner, the receiving unit 601 is further configured to receive a multicast QoS flow from a service server forwarded by the source base station, where the multicast QoS flow includes data of the first service;

[0206] The apparatus also includes: a processing unit (not shown in the figure), which is used to discard or reject the multicast QoS flow if the target base station does not support the multicast QoS flow, or convert the multicast QoS flow into a unicast QoS flow and send it to the terminal device.

[0207] In an optional manner, the receiving unit 601 is also used to receive a unicast QoS flow sent by the source base station, and the unicast QoS flow contains data of the first service; wherein the unicast QoS flow is obtained by converting the multicast QoS flow from the service server by the core network element.

[0208] In an optional manner, the receiving unit 601 is also used to receive a unicast QoS stream sent by the source base station, wherein the unicast QoS stream contains data of the first service; wherein the unicast QoS stream is obtained by the source base station converting a multicast QoS stream from a service server.

[0209] In an optional manner, the receiving unit 601 is further used to receive a first data stream forwarded by the source base station from a service server, and to receive a second data stream sent by the service server through a multicast tunnel; the data packet in the first data stream carries a first SN, and the data packet in the second data stream carries a second SN; wherein the first data stream and the second data stream belong to data streams of the first service;

[0210] The sending unit 602 is also used to schedule a third data stream for the terminal device through a unicast tunnel if the first SN is smaller than the second SN, and the third data stream carries a third SN; the rate of the third data stream is greater than the rate of the first data stream; and when the third SN is equal to the second SN, schedule the second data stream for the terminal device through a multicast tunnel.

[0211] In an optional manner, the receiving unit 601 is further used to receive a first data stream forwarded by the source base station from a service server, and to receive a second data stream sent by the service server through a multicast tunnel; the data packet in the first data stream carries a first SN, and the data packet in the second data stream carries a second SN; wherein the first data stream and the second data stream belong to data streams of the first service;

[0212] The apparatus further includes: a processing unit (not shown in the figure), configured to perform duplication detection on the first data stream and the second data stream through a PDCP entity to generate a third data stream if the first SN is greater than the second SN;

[0213] The sending unit 602 is further configured to schedule the third data stream for the terminal device via a multicast tunnel.

[0214] Those skilled in the art should understand that the relevant description of the above-mentioned data transmission device in the embodiment of the present application can be understood by referring to the relevant description of the data transmission method in the embodiment of the present application.

[0215] Figure 7The structure of the data transmission device according to the embodiment of the present application is shown in FIG. Figure 2 , applied to terminal devices such as Figure 7 As shown, the data transmission device includes:

[0216] The receiving unit 701 is configured to receive data of a first service sent by a source base station in a multicast manner;

[0217] A sending unit 702 is configured to send a handover confirmation message to the target base station after handover from the source base station to the target base station;

[0218] The receiving unit 701 is further configured to receive data of the first service sent by the target base station in a multicast manner or a unicast manner.

[0219] In an optional manner, the data of the first service is sent on the source base station side through a multicast session, and the data of the first service is sent on the target base station side through a multicast session or a unicast session.

[0220] Those skilled in the art should understand that the relevant description of the above-mentioned data transmission device in the embodiment of the present application can be understood by referring to the relevant description of the data transmission method in the embodiment of the present application.

[0221] Figure 8 800 is a schematic structural diagram of a communication device 800 provided in an embodiment of the present application. The communication device may be a terminal device or a network device. Figure 8 The communication device 800 shown includes a processor 810, and the processor 810 can call and run a computer program from a memory to implement the method in the embodiment of the present application.

[0222] Alternatively, if Figure 8 As shown, the communication device 800 may further include a memory 820. The processor 810 may call and run a computer program from the memory 820 to implement the method in the embodiment of the present application.

[0223] The memory 820 may be a separate device independent of the processor 810 , or may be integrated into the processor 810 .

[0224] Alternatively, if Figure 8 As shown, the communication device 800 may further include a transceiver 830, and the processor 810 may control the transceiver 830 to communicate with other devices, specifically, may send information or data to other devices, or receive information or data sent by other devices.

[0225] The transceiver 830 may include a transmitter and a receiver. The transceiver 830 may further include an antenna, and the number of the antennas may be one or more.

[0226] Optionally, the communication device 800 may specifically be a network device of an embodiment of the present application, and the communication device 800 may implement the corresponding processes implemented by the network device in each method of the embodiment of the present application, which will not be described in detail here for the sake of brevity.

[0227] Optionally, the communication device 800 may specifically be a mobile terminal / terminal device of an embodiment of the present application, and the communication device 800 may implement the corresponding processes implemented by the mobile terminal / terminal device in each method of the embodiment of the present application, which will not be described in detail here for the sake of brevity.

[0228] Fig. 9 It is a schematic structural diagram of the chip of an embodiment of the present application. Fig. 9 The chip 900 shown includes a processor 910, which can call and run a computer program from a memory to implement the method in the embodiment of the present application.

[0229] Alternatively, if Fig. 9 As shown, the chip 900 may further include a memory 920. The processor 910 may call and run a computer program from the memory 920 to implement the method in the embodiment of the present application.

[0230] The memory 920 may be a separate device independent of the processor 910 , or may be integrated into the processor 910 .

[0231] Optionally, the chip 900 may further include an input interface 930. The processor 910 may control the input interface 930 to communicate with other devices or chips, and specifically, may obtain information or data sent by other devices or chips.

[0232] Optionally, the chip 900 may further include an output interface 940. The processor 910 may control the output interface 940 to communicate with other devices or chips, and specifically, may output information or data to other devices or chips.

[0233] Optionally, the chip can be applied to the network device in the embodiments of the present application, and the chip can implement the corresponding processes implemented by the network device in each method of the embodiments of the present application. For the sake of brevity, they will not be repeated here.

[0234] Optionally, the chip can be applied to the mobile terminal / terminal device in the embodiments of the present application, and the chip can implement the corresponding processes implemented by the mobile terminal / terminal device in the various methods of the embodiments of the present application. For the sake of brevity, they will not be repeated here.

[0235] It should be understood that the chip mentioned in the embodiments of the present application can also be called a system-level chip, a system chip, a chip system or a system-on-chip chip, etc.

[0236] Fig.10 1 is a schematic block diagram of a communication system 1000 provided in an embodiment of the present application. Fig.10 As shown, the communication system 1000 includes a terminal device 1010 and a network device 1020 .

[0237] Among them, the terminal device 1010 can be used to implement the corresponding functions implemented by the terminal device in the above method, and the network device 1020 can be used to implement the corresponding functions implemented by the network device in the above method. For the sake of brevity, they are not repeated here.

[0238] It should be understood that the processor of the embodiment of the present application may be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method embodiment can be completed by the hardware integrated logic circuit or software instructions in the processor. The above processor can be a general processor, a digital signal processor (Digital Signal Processor, DSP), an application-specific integrated circuit (Application Specific Integrated Circuit, ASIC), a field programmable gate array (Field Programmable Gate Array, FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components. The methods, steps and logic block diagrams disclosed in the embodiments of the present application can be implemented or executed. The general processor can be a microprocessor or the processor can also be any conventional processor. The steps of the method disclosed in the embodiment of the present application can be directly embodied as a hardware decoding processor to perform, or the hardware and software modules in the decoding processor are combined and performed. The software module can be located in a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, and other mature storage media in the art. The storage medium is located in the memory, and the processor reads the information in the memory and completes the steps of the above method in combination with its hardware.

[0239] It can be understood that the memory in the embodiments of the present application can be a volatile memory or a non-volatile memory, or can include both volatile and non-volatile memories. Among them, the non-volatile memory can be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory can be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM), and direct RAM bus random access memory (DR RAM). It should be noted that the memory of the systems and methods described herein is intended to include, but is not limited to, these and any other suitable types of memory.

[0240] It should be understood that the above-mentioned memory is exemplary but not restrictive. For example, the memory in the embodiments of the present application may also be static random access memory (static RAM, SRAM), dynamic random access memory (dynamic RAM, DRAM), synchronous dynamic random access memory (synchronous DRAM, SDRAM), double data rate synchronous dynamic random access memory (double data rate SDRAM, DDR SDRAM), enhanced synchronous dynamic random access memory (enhanced SDRAM, ESDRAM), synchronous link dynamic random access memory (synch link DRAM, SLDRAM) and direct memory bus random access memory (Direct Rambus RAM, DR RAM), etc. That is to say, the memory in the embodiments of the present application is intended to include but not limited to these and any other suitable types of memory.

[0241] An embodiment of the present application also provides a computer-readable storage medium for storing a computer program.

[0242] Optionally, the computer-readable storage medium can be applied to the network device in the embodiments of the present application, and the computer program enables the computer to execute the corresponding processes implemented by the network device in the various methods of the embodiments of the present application. For the sake of brevity, they are not repeated here.

[0243] Optionally, the computer-readable storage medium can be applied to the mobile terminal / terminal device in the embodiments of the present application, and the computer program enables the computer to execute the corresponding processes implemented by the mobile terminal / terminal device in the various methods of the embodiments of the present application. For the sake of brevity, they are not repeated here.

[0244] An embodiment of the present application also provides a computer program product, including computer program instructions.

[0245] Optionally, the computer program product can be applied to the network device in the embodiments of the present application, and the computer program instructions enable the computer to execute the corresponding processes implemented by the network device in the various methods of the embodiments of the present application. For the sake of brevity, they are not repeated here.

[0246] Optionally, the computer program product can be applied to the mobile terminal / terminal device in the embodiments of the present application, and the computer program instructions enable the computer to execute the corresponding processes implemented by the mobile terminal / terminal device in the various methods of the embodiments of the present application. For the sake of brevity, they are not repeated here.

[0247] The embodiment of the present application also provides a computer program.

[0248] Optionally, the computer program can be applied to the network device in the embodiments of the present application. When the computer program runs on a computer, the computer executes the corresponding processes implemented by the network device in the various methods in the embodiments of the present application. For the sake of brevity, they are not described here.

[0249] Optionally, the computer program can be applied to the mobile terminal / terminal device in the embodiments of the present application. When the computer program runs on the computer, the computer executes the corresponding processes implemented by the mobile terminal / terminal device in the various methods of the embodiments of the present application. For the sake of brevity, they are not repeated here.

[0250] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0251] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0252] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0253] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0254] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0255] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0256] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A data transmission method, the method comprising: After receiving the switching confirmation message sent by the terminal device, the target base station sends the data of the first service to the terminal device, where the switching confirmation message is used to indicate that the terminal device confirms switching from the source base station to the target base station; wherein the data of the first service is sent by multicast at the source base station side, and the data of the first service is sent by multicast or unicast at the target base station side; The target base station receives a first data stream forwarded by the source base station from a service server, and receives a second data stream sent by the service server through a multicast tunnel; the data packets in the first data stream carry a first sequence number SN, and the data packets in the second data stream carry a second SN; wherein the first data stream and the second data stream belong to data streams of the first service; If the first SN is less than the second SN, the target base station schedules a third data stream for the terminal device through a unicast tunnel, and the third data stream carries a third SN; the rate of the third data stream is greater than the rate of the first data stream; When the third SN is equal to the second SN, the target base station schedules the second data stream for the terminal device through a multicast tunnel.

2. The method according to claim 1, wherein: The data of the first service is sent at the source base station side through a multicast session, and the data of the first service is sent at the target base station side through a multicast session or a unicast session.

3. The method according to claim 1 or 2, wherein: The method further comprises: The target base station receives a first message sent by a core network element, where the first message includes a context of a multicast session.

4. The method according to claim 3, wherein: The data of the first service is sent by multicast at the source base station side, and the data of the first service is sent by multicast at the target base station side: If the multicast session already exists on the target base station side, the context of the multicast session includes at least one of the following: an identifier of the terminal device, a group identifier of the multicast group to which the terminal device belongs, an identifier of the multicast session, and multicast quality of service QoS flow information; or, If the multicast session does not exist on the target base station side, the context of the multicast session includes at least one of the following: the identifier of the terminal device, the group identifier of the multicast group to which the terminal device belongs, the identifier of the multicast session, multicast QoS flow information, N3 UP address, and the tunnel identifier associated with the multicast session.

5. The method according to claim 1 or 2, wherein: The method further comprises: The target base station receives a second message sent by a core network element, where the second message includes a context of a unicast session.

6. The method according to claim 5, wherein: In the case where the data of the first service is sent by multicast at the source base station side and the data of the first service is sent by unicast at the target base station side: The context of the unicast session includes at least one of the following: an N3 UP address, a tunnel identifier associated with the unicast session, and unicast QoS flow information.

7. The method according to claim 1 or 2, wherein: The method further comprises: The target base station receives a third message sent by a core network element, where the third message includes a context of a multicast session and a context of a unicast session.

8. The method according to claim 7, wherein: The method further comprises: If the target base station supports the multicast session and accepts the multicast session, the target base station sends first indication information to the core network element, where the first indication information is used to instruct the target base station to accept the multicast session and reject the unicast session.

9. The method according to claim 7, wherein: The method further comprises: If the target base station does not support the multicast session or does not accept the multicast session, the target base station sends second indication information to the core network element, where the second indication information is used to indicate that the target base station does not support the multicast session or does not accept the multicast session.

10. The method according to claim 9, wherein: The method further comprises: The target base station stores the context of the multicast session; or, The target base station deletes the context of the multicast session.

11. The method according to claim 7, wherein: The method further comprises: The target base station stores the context of the multicast session and the context of the unicast session; If the target base station uses the context of the multicast session, the target base station sends third indication information to the core network element, where the third indication information is used to instruct the target base station to use the context of the multicast session; or, If the target base station uses the context of the unicast session, the target base station sends fourth indication information to the core network element, where the fourth indication information is used to instruct the target base station to use the context of the unicast session.

12. The method according to any one of claims 1, 2, 4, 6, 8 to 11, wherein: Before the target base station receives the handover confirmation message sent by the terminal device, the method further includes: The target base station receives a multicast QoS flow from a service server forwarded by the source base station, where the multicast QoS flow includes data of the first service; If the target base station does not support the multicast QoS flow, the target base station discards or rejects the multicast QoS flow, or the target base station converts the multicast QoS flow into a unicast QoS flow and sends it to the terminal device.

13. The method according to any one of claims 1, 2, 4, 6, 8 to 11, wherein: Before the target base station receives the handover confirmation message sent by the terminal device, the method further includes: The target base station receives a unicast QoS flow sent by the source base station, where the unicast QoS flow includes data of the first service; wherein the unicast QoS flow is obtained by converting a multicast QoS flow from a service server by a core network element.

14. The method according to any one of claims 1, 2, 4, 6, 8 to 11, wherein: Before the target base station receives the handover confirmation message sent by the terminal device, the method further includes: The target base station receives a unicast QoS flow sent by the source base station, where the unicast QoS flow includes data of the first service; wherein the unicast QoS flow is obtained by the source base station converting a multicast QoS flow from a service server.

15. The method according to any one of claims 1, 2, 4, 6, 8 to 11, wherein: The method further comprises: If the first SN is greater than the second SN, the target base station performs repeated detection on the first data stream and the second data stream through a packet data convergence protocol PDCP entity to generate a third data stream; the target base station schedules the third data stream for the terminal device through a multicast tunnel.

16. A data transmission device, applied to a target base station, the device comprising: A receiving unit, configured to receive a switching confirmation message sent by a terminal device; The handover confirmation message is used to indicate that the terminal device confirms handover from the source base station to the target base station; A sending unit, configured to send data of a first service to the terminal device; wherein the data of the first service is sent by multicast at the source base station side, and the data of the first service is sent by multicast or unicast at the target base station side; The receiving unit is further configured to receive a first data stream forwarded by the source base station from a service server, and to receive a second data stream sent by the service server through a multicast tunnel; the data packets in the first data stream carry a first SN, and the data packets in the second data stream carry a second SN; wherein the first data stream and the second data stream belong to data streams of the first service; The sending unit is also used to schedule a third data stream for the terminal device through a unicast tunnel if the first SN is smaller than the second SN, and the third data stream carries a third SN; the rate of the third data stream is greater than the rate of the first data stream; and when the third SN is equal to the second SN, schedule the second data stream for the terminal device through a multicast tunnel.

17. The device according to claim 16, wherein: The data of the first service is sent at the source base station side through a multicast session, and the data of the first service is sent at the target base station side through a multicast session or a unicast session.

18. The device according to claim 16 or 17, wherein: The receiving unit is further configured to receive a first message sent by a core network element, where the first message includes the context of the multicast session.

19. The device according to claim 18, wherein: The data of the first service is sent by multicast at the source base station side, and the data of the first service is sent by multicast at the target base station side: If the multicast session already exists on the target base station side, the context of the multicast session includes at least one of the following: an identifier of the terminal device, a group identifier of the multicast group to which the terminal device belongs, an identifier of the multicast session, and multicast QoS flow information; or, If the multicast session does not exist on the target base station side, the context of the multicast session includes at least one of the following: the identifier of the terminal device, the group identifier of the multicast group to which the terminal device belongs, the identifier of the multicast session, multicast QoS flow information, N3 UP address, and the tunnel identifier associated with the multicast session.

20. The device according to claim 16 or 17, wherein: The receiving unit is further configured to receive a second message sent by a core network element, where the second message includes a context of a unicast session.

21. The device according to claim 20, wherein: In the case where the data of the first service is sent by multicast at the source base station side and the data of the first service is sent by unicast at the target base station side: The context of the unicast session includes at least one of the following: an N3 UP address, a tunnel identifier associated with the unicast session, and unicast QoS flow information.

22. The device according to claim 16 or 17, wherein: The receiving unit is further configured to receive a third message sent by a core network element, wherein the third message includes a context of a multicast session and a context of a unicast session.

23. The device according to claim 22, wherein: The sending unit is further used to send first indication information to the core network element if the target base station supports the multicast session and accepts the multicast session, wherein the first indication information is used to instruct the target base station to accept the multicast session and reject the unicast session.

24. The device according to claim 22, wherein: The sending unit is further used to send second indication information to the core network element if the target base station does not support the multicast session or does not accept the multicast session, wherein the second indication information is used to indicate that the target base station does not support the multicast session or does not accept the multicast session.

25. The device according to claim 24, wherein: The device also includes: The processing unit is configured to store the context of the multicast session; or delete the context of the multicast session.

26. The device according to claim 22, wherein: The device also includes: a processing unit, configured to store the context of the multicast session and the context of the unicast session; The sending unit is also used to send third indication information to the core network network element if the target base station uses the context of the multicast session; the third indication information is used to instruct the target base station to use the context of the multicast session; or, if the target base station uses the context of the unicast session, send fourth indication information to the core network network element, the fourth indication information is used to instruct the target base station to use the context of the unicast session.

27. The device according to any one of claims 16, 17, 19, 21, 23 to 26, wherein The receiving unit is further configured to receive a multicast QoS flow from a service server forwarded by the source base station, wherein the multicast QoS flow includes data of the first service; The apparatus further includes: a processing unit, configured to discard or reject the multicast QoS flow if the target base station does not support the multicast QoS flow, or convert the multicast QoS flow into a unicast QoS flow and send it to the terminal device.

28. The device according to any one of claims 16, 17, 19, 21, 23 to 26, wherein The receiving unit is further used to receive a unicast QoS flow sent by the source base station, wherein the unicast QoS flow contains data of the first service; wherein the unicast QoS flow is obtained by converting a multicast QoS flow from a service server by a core network element.

29. The device according to any one of claims 16, 17, 19, 21, 23 to 26, wherein The receiving unit is further used to receive a unicast QoS flow sent by the source base station, where the unicast QoS flow contains data of the first service; wherein the unicast QoS flow is obtained by the source base station converting a multicast QoS flow from a service server.

30. The device according to any one of claims 16, 17, 19, 21, 23 to 26, wherein The apparatus further includes: a processing unit, configured to perform duplication detection on the first data stream and the second data stream through a PDCP entity to generate a third data stream if the first SN is greater than the second SN; The sending unit is further used to schedule the third data stream for the terminal device through a multicast tunnel.

31. A network device comprising: A processor and a memory, the memory being used to store a computer program, the processor being used to call and run the computer program stored in the memory to execute the method according to any one of claims 1 to 15.

32. A chip, comprising: A processor, configured to call and run a computer program from a memory, so that a device equipped with the chip executes a method as claimed in any one of claims 1 to 15.

33. A computer-readable storage medium for storing a computer program, wherein the computer program causes a computer to execute the method according to any one of claims 1 to 15.

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